corstone1000: add compressed kernel support

unzip the kernel before executing it

The Corstone-1000 kernel has become too large to fit in the available
storage.  Switching to a compressed kernel avoids the problem, but
requires uncompressing it.

Changes made are generated using savedefconfig.

Signed-off-by: Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>
Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>